A doser-dispenser envisaged by the present invention comprises a doser unit in the housing of which are provided, on the one hand, an upper supply chamber connected by a supply conduit to said first reservoir and, on the other hand, a lower dosing chamber separated from said supply chamber by a doser-piston which is fixed to the lower end of a supporting stirrup element fast, at its other end, with the lower end of a first control tube penetrating in tight manner in said first housing. This doser-piston slides in tight manner in the first housing and is provided with a central passage adapted to be obturated by an intake valve of which the obturation member, such as a flap, is borne by the free end of a second control tube or rod projecting in tight manner from the lower end of the first control tube and associated with control means distinct from the device for controlling the first control tube. This second tube is urged by a return spring in the direction of closure of the intake valve, is guided with respect to said doser-piston and cooperates with a valve seat surrounding said central passage of the doser-piston. The doser-dispenser also comprises at least one dispenser unit comprising a dispensing chamber of which the inlet is connected to the outlet of the dosing chamber and of which the outlet is connected to at least one ejection tube, as well as an ejection valve of which the obturation member, such as a flap or membrane, cooperates with the upstream end of each ejection tube, end constituting the seat of said ejection valve and is associated with a control unit.
Such a doser-dispenser is described in French Patent Application FR-A-89 06316 of May 12, 1989.
It has proved to be difficult to dispense with such a doser-dispenser doses of product which are very precise from one dose to the other as soon as each dose represents only a small quantity for which the normal imprecision of the doser-dispenser exceeds 1 to 2% by weight of the predetermined reference dose. This drawback is manifest when the recipients of a row of recipients must be filled simultaneously with doses of product identical from one recipient to the other, with the aid of a doser-dispenser assembly presenting as many doser-dispensers as there are recipients in a row of recipients. Doser-dispensers may, of course, be made whose dosing chambers and doser-pistons all present the same dimensions, but such production involves a prohibitive cost price.
It is an object of the invention to overcome or at least attenuate these drawbacks.